Case study

Ipswich Motorway Upgrade

ProjectIpswich Motorway Upgrade Six Mile Creek Bridges Hydraulic Investigation
ClientCarter Newell Lawyers (on behalf of Zurich Ireland Ltd, the lead insurer of the Ipswich Motorway Upgrade Origin Alliance)
LocationNear Ipswich, Queensland
Disciplines/ServicePeer Review
Hydrological Modelling
Hydraulic Modelling
Hydraulic Design of Bridges
WRM ContactDr Sharmil Markar

The Challenge

The Ipswich Motorway Upgrade Project (IMUP) was completed by the Origin Alliance in May 2012 and included a significant reconfiguration of the existing Six Mile Creek bridge crossings. In October 2009 (during the construction period), a major stress crack was located along the face of an abutment of one of the Motorway bridges, resulting in the redesign and reconstruction of the abutment, including a reconfiguration of the abutment geometry and the inclusion of ground reinforcing piles.
Subsequently during the January 2011 flood event, damage was observed at the abutments of several of the Six Mile Creek bridges and remedial works were required to repair the damage.

The four bridges under investigation were across Six Mile Creek near its confluence with the Brisbane River and located in close proximity to each other. Therefore the hydraulic designs of these bridges have to take into account both the Brisbane River (regional) and Six Mile Creek (local) flooding. The key challenge of this project was to understand and model the complex hydraulics that occurs when bridges are in close proximity.

Approach and Key Activities

WRM was requested to investigate and provide expert opinion on:

  • The adequacy of the original hydraulic designs for the Six Mile Creek bridge crossings;
  • Compliance of the original hydraulic designs with relevant hydraulic design criteria; and
  • The impact of the redesign of the bridge abutments following the January 2011 flood on the hydraulic adequacy of the bridges.

Hydraulic modelling to determine local flood levels, velocities, scour potential and afflux at the Six Mile Creek bridge crossings was undertaken to accurately assess the hydraulic designs and flood impacts.


Requested expert opinion was provided to the client based on detailed hydrologic and hydraulic modelling.